I think 77-78 is perfect. Higher temps will increase his metabolism and growth but believe it's healthier long term the way you had it. But 79 is not to high to cause concern as metnioned above
I agree with this, I run between 76, and 79. fish fine all way up to 87 to 90, but they allot more frisky, hungry, upper 70ies are the right place to be IMHO.
I used to keep my gt's at around 75, 76.
They grew well and spawned often at these temps.
I think a lot of species are kept too warm.
Cooler water holds more oxygen.In higher temps metabolism speeds up and they eat and crap more.
Unless I am keeping very warm water fish like rams or discus, I aim for the cooler end of the temp range.
It's also more economical.
I believe most aquarists these days keep their fish in much higher temps than needed, or is healthy. All animals have an optimum range they have evolved to live within.
If you google water temps of the rivers west of the Andes, you may be surprised to find the "average" is in the low to mid to 70sF. Higher at certain times of the year (the dry season), lower at others (the rainy season) .
So to me temps around 80'F are pushing the envelope for many species from that area.
You may see faster growth, and more aggression but may also be creating slight stress, which can be a the cause for disease.
I was in Colombia a few months back in an area fed by the Magdalena river system, which begins in the nearby Sierra Nevada de Santa Marta mountain range, and it is covered in glaciers. Even near where the mountains emptied into the sea, the water was "not" by any stretch of the imagination, warm.